<?php

/**
 * @file
 * Functions to handle paths in Drupal, including path aliasing.
 *
 * These functions are not loaded for cached pages, but modules that need
 * to use them in hook_boot() or hook exit() can make them available, by
 * executing "drupal_bootstrap(DRUPAL_BOOTSTRAP_FULL);".
 */

/**
 * Initialize the $_GET['q'] variable to the proper normal path.
 */
function drupal_path_initialize() {
	// Ensure $_GET['q'] is set before calling drupal_normal_path(), to support
	// path caching with hook_url_inbound_alter().
	if (empty($_GET['q'])) {
		$_GET['q'] = variable_get('site_frontpage', 'node');
	}
	$_GET['q'] = drupal_get_normal_path($_GET['q']);
}

/**
 * Given an alias, return its Drupal system URL if one exists. Given a Drupal
 * system URL return one of its aliases if such a one exists. Otherwise,
 * return FALSE.
 *
 * @param $action
 *   One of the following values:
 *   - wipe: delete the alias cache.
 *   - alias: return an alias for a given Drupal system path (if one exists).
 *   - source: return the Drupal system URL for a path alias (if one exists).
 * @param $path
 *   The path to investigate for corresponding aliases or system URLs.
 * @param $path_language
 *   Optional language code to search the path with. Defaults to the page language.
 *   If there's no path defined for that language it will search paths without
 *   language.
 *
 * @return
 *   Either a Drupal system path, an aliased path, or FALSE if no path was
 *   found.
 */
function drupal_lookup_path($action, $path = '', $path_language = NULL) {
	global $language_url;
	// Use the advanced drupal_static() pattern, since this is called very often.
	static $drupal_static_fast;
	if (!isset($drupal_static_fast)) {
		$drupal_static_fast['cache'] = &drupal_static(__FUNCTION__);
	}
	$cache = &$drupal_static_fast['cache'];

	if (!isset($cache)) {
		$cache = array(
				'map' => array(),
				'no_source' => array(),
				'whitelist' => NULL,
				'system_paths' => array(),
				'no_aliases' => array(),
				'first_call' => TRUE,
		);
	}

	// Retrieve the path alias whitelist.
	if (!isset($cache['whitelist'])) {
		$cache['whitelist'] = variable_get('path_alias_whitelist', NULL);
		if (!isset($cache['whitelist'])) {
			$cache['whitelist'] = drupal_path_alias_whitelist_rebuild();
		}
	}

	// If no language is explicitly specified we default to the current URL
	// language. If we used a language different from the one conveyed by the
	// requested URL, we might end up being unable to check if there is a path
	// alias matching the URL path.
	$path_language = $path_language ? $path_language : $language_url->language;

	if ($action == 'wipe') {
		$cache = array();
		$cache['whitelist'] = drupal_path_alias_whitelist_rebuild();
	}
	elseif ($cache['whitelist'] && $path != '') {
		if ($action == 'alias') {
			// During the first call to drupal_lookup_path() per language, load the
			// expected system paths for the page from cache.
			if (!empty($cache['first_call'])) {
				$cache['first_call'] = FALSE;

				$cache['map'][$path_language] = array();
				// Load system paths from cache.
				$cid = current_path();
				if ($cached = cache_get($cid, 'cache_path')) {
					$cache['system_paths'] = $cached->data;
					// Now fetch the aliases corresponding to these system paths.
					$args = array(
							':system' => $cache['system_paths'],
							':language' => $path_language,
							':language_none' => LANGUAGE_NONE,
					);
					// Always get the language-specific alias before the language-neutral
					// one. For example 'de' is less than 'und' so the order needs to be
					// ASC, while 'xx-lolspeak' is more than 'und' so the order needs to
					// be DESC. We also order by pid ASC so that fetchAllKeyed() returns
					// the most recently created alias for each source. Subsequent queries
					// using fetchField() must use pid DESC to have the same effect.
					// For performance reasons, the query builder is not used here.
					if ($path_language == LANGUAGE_NONE) {
						// Prevent PDO from complaining about a token the query doesn't use.
						unset($args[':language']);
						$result = db_query('SELECT source, alias FROM {url_alias} WHERE source IN (:system) AND language = :language_none ORDER BY pid ASC', $args);
					}
					elseif ($path_language < LANGUAGE_NONE) {
						$result = db_query('SELECT source, alias FROM {url_alias} WHERE source IN (:system) AND language IN (:language, :language_none) ORDER BY language ASC, pid ASC', $args);
					}
					else {
						$result = db_query('SELECT source, alias FROM {url_alias} WHERE source IN (:system) AND language IN (:language, :language_none) ORDER BY language DESC, pid ASC', $args);
					}
					$cache['map'][$path_language] = $result->fetchAllKeyed();
					// Keep a record of paths with no alias to avoid querying twice.
					$cache['no_aliases'][$path_language] = array_flip(array_diff_key($cache['system_paths'], array_keys($cache['map'][$path_language])));
				}
			}
			// If the alias has already been loaded, return it.
			if (isset($cache['map'][$path_language][$path])) {
				return $cache['map'][$path_language][$path];
			}
			// Check the path whitelist, if the top_level part before the first /
			// is not in the list, then there is no need to do anything further,
			// it is not in the database.
			elseif (!isset($cache['whitelist'][strtok($path, '/')])) {
				return FALSE;
			}
			// For system paths which were not cached, query aliases individually.
			elseif (!isset($cache['no_aliases'][$path_language][$path])) {
				$args = array(
						':source' => $path,
						':language' => $path_language,
						':language_none' => LANGUAGE_NONE,
				);
				// See the queries above.
				if ($path_language == LANGUAGE_NONE) {
					unset($args[':language']);
					$alias = db_query("SELECT alias FROM {url_alias} WHERE source = :source AND language = :language_none ORDER BY pid DESC", $args)->fetchField();
				}
				elseif ($path_language > LANGUAGE_NONE) {
					$alias = db_query("SELECT alias FROM {url_alias} WHERE source = :source AND language IN (:language, :language_none) ORDER BY language DESC, pid DESC", $args)->fetchField();
				}
				else {
					$alias = db_query("SELECT alias FROM {url_alias} WHERE source = :source AND language IN (:language, :language_none) ORDER BY language ASC, pid DESC", $args)->fetchField();
				}
				$cache['map'][$path_language][$path] = $alias;
				return $alias;
			}
		}
		// Check $no_source for this $path in case we've already determined that there
		// isn't a path that has this alias
		elseif ($action == 'source' && !isset($cache['no_source'][$path_language][$path])) {
			// Look for the value $path within the cached $map
			$source = FALSE;
			if (!isset($cache['map'][$path_language]) || !($source = array_search($path, $cache['map'][$path_language]))) {
				$args = array(
						':alias' => $path,
						':language' => $path_language,
						':language_none' => LANGUAGE_NONE,
				);
				// See the queries above.
				if ($path_language == LANGUAGE_NONE) {
					unset($args[':language']);
					$result = db_query("SELECT source FROM {url_alias} WHERE alias = :alias AND language = :language_none ORDER BY pid DESC", $args);
				}
				elseif ($path_language > LANGUAGE_NONE) {
					$result = db_query("SELECT source FROM {url_alias} WHERE alias = :alias AND language IN (:language, :language_none) ORDER BY language DESC, pid DESC", $args);
				}
				else {
					$result = db_query("SELECT source FROM {url_alias} WHERE alias = :alias AND language IN (:language, :language_none) ORDER BY language ASC, pid DESC", $args);
				}
				if ($source = $result->fetchField()) {
					$cache['map'][$path_language][$source] = $path;
				}
				else {
					// We can't record anything into $map because we do not have a valid
					// index and there is no need because we have not learned anything
					// about any Drupal path. Thus cache to $no_source.
					$cache['no_source'][$path_language][$path] = TRUE;
				}
			}
			return $source;
		}
	}

	return FALSE;
}

/**
 * Cache system paths for a page.
 *
 * Cache an array of the system paths available on each page. We assume
 * that aliases will be needed for the majority of these paths during
 * subsequent requests, and load them in a single query during
 * drupal_lookup_path().
 */
function drupal_cache_system_paths() {
	// Check if the system paths for this page were loaded from cache in this
	// request to avoid writing to cache on every request.
	$cache = &drupal_static('drupal_lookup_path', array());
	if (empty($cache['system_paths']) && !empty($cache['map'])) {
		// Generate a cache ID (cid) specifically for this page.
		$cid = current_path();
		// The static $map array used by drupal_lookup_path() includes all
		// system paths for the page request.
		if ($paths = current($cache['map'])) {
			$data = array_keys($paths);
			$expire = REQUEST_TIME + (60 * 60 * 24);
			cache_set($cid, $data, 'cache_path', $expire);
		}
	}
}

/**
 * Given an internal Drupal path, return the alias set by the administrator.
 *
 * If no path is provided, the function will return the alias of the current
 * page.
 *
 * @param $path
 *   An internal Drupal path.
 * @param $path_language
 *   An optional language code to look up the path in.
 *
 * @return
 *   An aliased path if one was found, or the original path if no alias was
 *   found.
 */
function drupal_get_path_alias($path = NULL, $path_language = NULL) {
	// If no path is specified, use the current page's path.
	if ($path == NULL) {
		$path = $_GET['q'];
	}
	$result = $path;
	if ($alias = drupal_lookup_path('alias', $path, $path_language)) {
		$result = $alias;
	}
	return $result;
}

/**
 * Given a path alias, return the internal path it represents.
 *
 * @param $path
 *   A Drupal path alias.
 * @param $path_language
 *   An optional language code to look up the path in.
 *
 * @return
 *   The internal path represented by the alias, or the original alias if no
 *   internal path was found.
 */
function drupal_get_normal_path($path, $path_language = NULL) {
	$original_path = $path;

	// Lookup the path alias first.
	if ($source = drupal_lookup_path('source', $path, $path_language)) {
		$path = $source;
	}

	// Allow other modules to alter the inbound URL. We cannot use drupal_alter()
	// here because we need to run hook_url_inbound_alter() in the reverse order
	// of hook_url_outbound_alter().
	foreach (array_reverse(module_implements('url_inbound_alter')) as $module) {
		$function = $module . '_url_inbound_alter';
		$function($path, $original_path, $path_language);
	}

	return $path;
}

/**
 * Check if the current page is the front page.
 *
 * @return
 *   Boolean value: TRUE if the current page is the front page; FALSE if otherwise.
 */
function drupal_is_front_page() {
	// Use the advanced drupal_static() pattern, since this is called very often.
	static $drupal_static_fast;
	if (!isset($drupal_static_fast)) {
		$drupal_static_fast['is_front_page'] = &drupal_static(__FUNCTION__);
	}
	$is_front_page = &$drupal_static_fast['is_front_page'];

	if (!isset($is_front_page)) {
		// As drupal_path_initialize updates $_GET['q'] with the 'site_frontpage' path,
		// we can check it against the 'site_frontpage' variable.
		$is_front_page = ($_GET['q'] == variable_get('site_frontpage', 'node'));
	}

	return $is_front_page;
}

/**
 * Check if a path matches any pattern in a set of patterns.
 *
 * @param $path
 *   The path to match.
 * @param $patterns
 *   String containing a set of patterns separated by \n, \r or \r\n.
 *
 * @return
 *   Boolean value: TRUE if the path matches a pattern, FALSE otherwise.
 */
function drupal_match_path($path, $patterns) {
	$regexps = &drupal_static(__FUNCTION__);

	if (!isset($regexps[$patterns])) {
		// Convert path settings to a regular expression.
		// Therefore replace newlines with a logical or, /* with asterisks and the <front> with the frontpage.
		$to_replace = array(
				'/(\r\n?|\n)/', // newlines
				'/\\\\\*/',     // asterisks
				'/(^|\|)\\\\<front\\\\>($|\|)/' // <front>
		);
		$replacements = array(
				'|',
				'.*',
				'\1' . preg_quote(variable_get('site_frontpage', 'node'), '/') . '\2'
		);
		$patterns_quoted = preg_quote($patterns, '/');
		$regexps[$patterns] = '/^(' . preg_replace($to_replace, $replacements, $patterns_quoted) . ')$/';
	}
	return (bool)preg_match($regexps[$patterns], $path);
}

/**
 * Return the current URL path of the page being viewed.
 *
 * Examples:
 * - http://example.com/node/306 returns "node/306".
 * - http://example.com/drupalfolder/node/306 returns "node/306" while
 *   base_path() returns "/drupalfolder/".
 * - http://example.com/path/alias (which is a path alias for node/306) returns
 *   "node/306" as opposed to the path alias.
 *
 * This function is not available in hook_boot() so use $_GET['q'] instead.
 * However, be careful when doing that because in the case of Example #3
 * $_GET['q'] will contain "path/alias". If "node/306" is needed, calling
 * drupal_bootstrap(DRUPAL_BOOTSTRAP_FULL) makes this function available.
 *
 * @return
 *   The current Drupal URL path.
 *
 * @see request_path()
 */
function current_path() {
	return $_GET['q'];
}

/**
 * Rebuild the path alias white list.
 *
 * @param $source
 *   An optional system path for which an alias is being inserted.
 *
 * @return
 *   An array containing a white list of path aliases.
 */
function drupal_path_alias_whitelist_rebuild($source = NULL) {
	// When paths are inserted, only rebuild the whitelist if the system path
	// has a top level component which is not already in the whitelist.
	if (!empty($source)) {
		$whitelist = variable_get('path_alias_whitelist', NULL);
		if (isset($whitelist[strtok($source, '/')])) {
			return $whitelist;
		}
	}
	// For each alias in the database, get the top level component of the system
	// path it corresponds to. This is the portion of the path before the first
	// '/', if present, otherwise the whole path itself.
	$whitelist = array();
	$result = db_query("SELECT DISTINCT SUBSTRING_INDEX(source, '/', 1) AS path FROM {url_alias}");
	foreach ($result as $row) {
		$whitelist[$row->path] = TRUE;
	}
	variable_set('path_alias_whitelist', $whitelist);
	return $whitelist;
}

/**
 * Fetch a specific URL alias from the database.
 *
 * @param $conditions
 *   A string representing the source, a number representing the pid, or an
 *   array of query conditions.
 *
 * @return
 *   FALSE if no alias was found or an associative array containing the
 *   following keys:
 *   - source: The internal system path.
 *   - alias: The URL alias.
 *   - pid: Unique path alias identifier.
 *   - language: The language of the alias.
 */
function path_load($conditions) {
	if (is_numeric($conditions)) {
		$conditions = array('pid' => $conditions);
	}
	elseif (is_string($conditions)) {
		$conditions = array('source' => $conditions);
	}
	elseif (!is_array($conditions)) {
		return FALSE;
	}
	$select = db_select('url_alias');
	foreach ($conditions as $field => $value) {
		$select->condition($field, $value);
	}
	return $select
	->fields('url_alias')
	->execute()
	->fetchAssoc();
}

/**
 * Save a path alias to the database.
 *
 * @param $path
 *   An associative array containing the following keys:
 *   - source: The internal system path.
 *   - alias: The URL alias.
 *   - pid: (optional) Unique path alias identifier.
 *   - language: (optional) The language of the alias.
 */
function path_save(&$path) {
	$path += array('pid' => NULL, 'language' => LANGUAGE_NONE);

	// Insert or update the alias.
	$status = drupal_write_record('url_alias', $path, (!empty($path['pid']) ? 'pid' : array()));

	// Verify that a record was written.
	if ($status) {
		if ($status === SAVED_NEW) {
			module_invoke_all('path_insert', $path);
		}
		else {
			module_invoke_all('path_update', $path);
		}
		drupal_clear_path_cache($path['source']);
	}
}

/**
 * Delete a URL alias.
 *
 * @param $criteria
 *   A number representing the pid or an array of criteria.
 */
function path_delete($criteria) {
	if (!is_array($criteria)) {
		$criteria = array('pid' => $criteria);
	}
	$path = path_load($criteria);
	$query = db_delete('url_alias');
	foreach ($criteria as $field => $value) {
		$query->condition($field, $value);
	}
	$query->execute();
	module_invoke_all('path_delete', $path);
	drupal_clear_path_cache($path['source']);
}

/**
 * Determine whether a path is in the administrative section of the site.
 *
 * By default, paths are considered to be non-administrative. If a path does not
 * match any of the patterns in path_get_admin_paths(), or if it matches both
 * administrative and non-administrative patterns, it is considered
 * non-administrative.
 *
 * @param $path
 *   A Drupal path.
 *
 * @return
 *   TRUE if the path is administrative, FALSE otherwise.
 *
 * @see path_get_admin_paths()
 * @see hook_admin_paths()
 * @see hook_admin_paths_alter()
 */
function path_is_admin($path) {
	$path_map = &drupal_static(__FUNCTION__);
	if (!isset($path_map['admin'][$path])) {
		$patterns = path_get_admin_paths();
		$path_map['admin'][$path] = drupal_match_path($path, $patterns['admin']);
		$path_map['non_admin'][$path] = drupal_match_path($path, $patterns['non_admin']);
	}
	return $path_map['admin'][$path] && !$path_map['non_admin'][$path];
}

/**
 * Get a list of administrative and non-administrative paths.
 *
 * @return array
 *   An associative array containing the following keys:
 *   'admin': An array of administrative paths and regular expressions
 *            in a format suitable for drupal_match_path().
 *   'non_admin': An array of non-administrative paths and regular expressions.
 *
 * @see hook_admin_paths()
 * @see hook_admin_paths_alter()
 */
function path_get_admin_paths() {
	$patterns = &drupal_static(__FUNCTION__);
	if (!isset($patterns)) {
		$paths = module_invoke_all('admin_paths');
		drupal_alter('admin_paths', $paths);
		// Combine all admin paths into one array, and likewise for non-admin paths,
		// for easier handling.
		$patterns = array();
		$patterns['admin'] = array();
		$patterns['non_admin'] = array();
		foreach ($paths as $path => $enabled) {
			if ($enabled) {
				$patterns['admin'][] = $path;
			}
			else {
				$patterns['non_admin'][] = $path;
			}
		}
		$patterns['admin'] = implode("\n", $patterns['admin']);
		$patterns['non_admin'] = implode("\n", $patterns['non_admin']);
	}
	return $patterns;
}

/**
 * Checks a path exists and the current user has access to it.
 *
 * @param $path
 *   The path to check.
 * @param $dynamic_allowed
 *   Whether paths with menu wildcards (like user/%) should be allowed.
 *
 * @return
 *   TRUE if it is a valid path AND the current user has access permission,
 *   FALSE otherwise.
 */
function drupal_valid_path($path, $dynamic_allowed = FALSE) {
	global $menu_admin;
	// We indicate that a menu administrator is running the menu access check.
	$menu_admin = TRUE;
	if ($path == '<front>' || url_is_external($path)) {
		$item = array('access' => TRUE);
	}
	elseif ($dynamic_allowed && preg_match('/\/\%/', $path)) {
		// Path is dynamic (ie 'user/%'), so check directly against menu_router table.
		if ($item = db_query("SELECT * FROM {menu_router} where path = :path", array(':path' => $path))->fetchAssoc()) {
			$item['link_path']  = $form_item['link_path'];
			$item['link_title'] = $form_item['link_title'];
			$item['external']   = FALSE;
			$item['options'] = '';
			_menu_link_translate($item);
		}
	}
	else {
		$item = menu_get_item($path);
	}
	$menu_admin = FALSE;
	return $item && $item['access'];
}

/**
 * Clear the path cache.
 *
 * @param $source
 *   An optional system path for which an alias is being changed.
 */
function drupal_clear_path_cache($source = NULL) {
	// Clear the drupal_lookup_path() static cache.
	drupal_static_reset('drupal_lookup_path');
	drupal_path_alias_whitelist_rebuild($source);
}
